1. Field of the Invention
The present invention relates to a polypeptide adjuvant composition, and in particular, to a polypeptide adjuvant composition with thermostability.
2. The Prior Arts
In March and April 1997, there were outbreaks of H5N1 avian influenza viruses on several poultry farms in the province of Hong Kong. These viruses were highly pathogenic in chickens and resulted in high mortality of infected chickens. During this same period, the continuing occurrence of infection of humans with influenza virus led to fears of a deadly influenza pandemic. It resulted in huge economic impact and financial crisis. The best way to prevent infection with avian influenza is to avoid sources of exposure whenever possible. Most bird infections with avian influenza in poultry farms will be culled to avoid the viruses spreading. However, in high-density poultry farms, once the high-pathogenic avian influenza outbreaks, the speed of culling the infected birds may be less than that of the high-pathogenic avian influenza spread. Vaccination is the most effective way to prevent infection and severe outcomes caused by influenza viruses. And it needs to step up the preventive measures against avian influenza.
Growth in the veterinary vaccines market is primarily attributed to augmented public awareness and technological innovations. Many newly developed vaccines are considered advantageous over traditional vaccines in terms of production volumes and immune response. Growing demand for the vaccines and increased vulnerability to diseases such as avian influenza, is steering the demand for veterinary vaccines in the emerging Asia-Pacific regions, Moreover, the altering patterns of diseases among animals and increased development of resistance to currently used antimicrobials is compelling manufacturers to invest heavily in new product developments.
For prevention of bird infection with avian influenza viruses, a vaccine with excellent quality may reduce the rate of the birds infected and the viruses transmitted. And it is very important to manufacture vaccine adjuvants which can enhance antigen-specific immune responses. Two main known vaccine adjuvants in livestock are aluminum-based and oil-based. The adverse effect of both vaccine adjuvants is chemical-makeup, wherein the aluminum-based adjuvant can not enhance the specificity of the Th1 cell immune response. Oil-based adjuvant can trigger immune system response, but it may result in local inflammation and granulomatous reactions at the site of injection, chronic inflammation, skin ulceration, local abscess or tissue sloughing, diffuse systemic granulomas, and it is also unable to enhance the production of antibodies.
Recently, the vaccine adjuvant has been improved to low or free oil-based, such as biological adjuvant and protein adjuvant. In the past, it is well known that mammalian interleukin-1β is pro-inflammatory cytokines involved in immune defense against infection. Interleukin-1β is mainly expressed by monocytes and macrophages and is synthesized as a precursor. The mature, bioactive interleukin-1β is produced upon caspase 1-mediated proteolysis of the precursor. The active interleukin-1β is then able to interact with type 1 interleukin-1 receptor and induce the expression of immune-related molecules such as cytokines and chemokines, thus triggering a cascade of immune responses. Therefore, interleukin-1β can be used as a vaccine adjuvant for vaccination to stimulate the secretion of chemotactic cytokine and the production of antibodies.
However, most adjuvants are unstable at about 46° C., and it needs to store at a lower temperature and to maintain the bioactivity of antigen and the good physical properties in the vaccine. However, there are heating steps (the range of 40° C. to 60° C.) in the manufacturing process of the protein adjuvant, and it is difficult to breakthrough the barrier of temperature. In addition, vaccines should be stored at the lower temperature from the time they are manufactured until the time them used. Overheating vaccines can cause obvious problem, as the protein in the vaccine will breakdown (denature) and will not produce the desired immune response. Therefore, it is necessary to manufacture a vaccine adjuvant with thermostability.
Interleukin-1β is mainly as a biological adjuvant, but its instability is limited the application. The present invention provides an improved circular permutation chicken interleukin-1β which is obtained by the combination of structural biology, biological information and genetic engineering. Because there are many protein adjuvants unstable at the temperature above 46° C., and chicken interleukin-1β is also included. The circular permutation chicken interleukin-1β of the present invention has been broken through the barrier which has not been overcome by other technology. Furthermore, the present invention also provides a most suitable condition to manufacture and purify the circular permutation chicken interleukin-1β, which is able to facilitate industrial applications.